Accident Description
While at approximately 500 feet above ground level and about 10 minutes from landing, the pilot noticed a change in main rotor noise. Subsequently, engine rpm increased while rotor rpm decreased. The pilot attempted to correct by reducing collective and increasing throttle, but engine rpm continued to rise and rotor rpm continued to drop. The pilot then entered an autorotation. During the autorotation, the helicopter impacted a wire and came to rest upright.
Post-Accident Inspection
Examination of the helicopter's mercury clutch revealed a 'minor' leak from the transmission sun gear seal, but no oil was found on the clutch shoes. The intermediate drive shaft teeth were 'severely' worn, with three teeth having broken corners. The clutch shoes were worn beyond limits and exhibited glazing consistent with overheating. One clutch return spring was broken. The driver slots in the clutch side plates were 'severely' worn, and the driver lugs were also 'severely' worn. All clutch attaching hardware were 'improperly' safetied, using .031 inch safety wire, and 'numerous' fasteners were safetied backwards. The clutch was a conditional item. Since the last 100-hour inspection on March 12, 1999, the helicopter had flown 100 hours.